An integrated circuit (IC) package encapsulates an IC chip (die) in a protective casing and may also provide power and signal distribution between the IC chip and an external printed circuit board (PCB). An IC package may use a metal lead frame to provide electrical paths for that distribution.
To facilitate discussion, FIG. 1 is a top view of a lead frame panel 100 made up for a plurality of lead frames that may be used in the prior art. The lead frame may comprise leads 108, die attach pads 112, ties 116 for supporting the die attach pads 112, and a skirt 120 for supporting the plurality of leads 108 and ties 116. The lead frame panel 100 may be etched or stamped from a thin sheet of metal. IC chips 124 may be mounted to the die attach pads 112 by an adhesive epoxy. Wire bonds 128, typically of fine gold wire, may then be added to electrically connect the IC chips 124 to the leads 108. Each IC chip 124 may then be encapsulated with part of the leads 108 and the die attach pad 112 in a protective casing, which may be produced by installing a preformed plastic or ceramic housing around each IC chip or by dispensing and molding a layer of encapsulating material over all IC chips 124. FIG. 2 is a cross-sectional view of part of the lead frame panel 100 and IC chips 124. In a process described in U.S. patent application Ser. No. 09/054,422, entitled “Lead Frame Chip Scale Package”, by Shahram Mostafazadeh et al., filed Apr. 2, 1998, a tape 136 is placed across the bottom of the lead frame panel 100 and an encapsulating process is used to encapsulate the IC chips 124, the wire bonds 128, and part of the lead frame panel 100. The tape 136 prevents the encapsulating material 140 from passing through the lead frame panel 100. Once the encapsulating material 140 is hardened, the tape 136 may be removed. The encapsulating material 140 may be cut to singulate the IC chips 124 and leads 108. The resulting singulated IC chips have leads with a length 155 which is substantially parallel to the conductive surface of the IC chips 124.
It is desirable to provide an IC package process which does not require the steps of creating wire bonds between the die and leads, adding tape to the lead frame, and then removing the tape from the lead frame. It is also desirable to provide a process and lead frame that provides lead fingers and a chip scale footprint.